Dynamic packet error management for wireless communications

ABSTRACT

Methods and apparatuses for dynamic error rate management. A wireless station may receive one or more data transfer parameters from another wireless station using a wireless communications protocol. Data may be selected to be transferred between the stations according to the wireless communications protocol based, at least in part, on the one or more data transfer parameters. The one or more data parameters may include a target packet error rate (PER).

This U.S. patent application is a divisional of U.S. patent applicationSer. No. 11/267,717 filed Nov. 4, 2005 now U.S. Pat. No. 7,499,426,filed concurrently herewith.

TECHNICAL FIELD

Embodiments of the invention relate to wireless networks. Moreparticularly, embodiments of the invention relate to wirelesscommunications conforming to Institute of Electrical and ElectronicsEngineers (IEEE) 802.16 standards.

BACKGROUND

Broadband wireless access may be used to provide mobile wide areanetwork access (e.g., Internet access) to locations that may or may nothave wired network access. A set of standards that define a strategy forbroadband wireless access include IEEE 802.16, which is often referredto as WiMAX, includes standards for various elements that may be used toprovide broadband wireless access.

IEEE 802.16 standards refer to, for example, Standard IEEE P802.16-2004,“Standard for Local and Metropolitan Area networks—Part 16: AirInterface for Fixed Broadband Wireless Access Systems,” and DraftStandard IEEE P802.16e/D12, “Amendment for Physical and Medium AccessControl Layers for Combined Fixed and Mobile Operation in LicensedBands,” and Draft Amendment IEEE 802.16g-05/0008r1, “Amendment to IEEEStandard for Local and Metropolitan Area Networks—Management PlaneProcedures and Services,” as well as related documents.

Most initial WiMAX deployments will be Point to Multipoint (PMP)networks based on centralized scheduling and radio resource managementin the base station (BS). The implication of this is that the BS may berequired to schedule grants on the uplink (UL) for the remote station(RS) to transmit. In a typical mobile/fixed WiMAX deployment, a RS mayhave multiple types of applications running concurrently. Differentapplications may require potentially different PER (Packet Error Rate)targets due to the fact that post-transmission link adaptationalgorithms can be used to improve performance with some impairments likelatency, which are problematic for voice but may be acceptable for dataapplications. Based on the UL signal to noise ratio (SNR) of the RS,these different PER targets can be translated to assigning differentModulation coding schemes (MCS) on the UL. The UL MCS is selected usingan UIUC (Uplink Interval Usage code).

Hence, a RS may use different UIUC for different applications orpotentially even for the same application. As an example, a single videostream may be split into multiple streams having associated connectionidentifiers (CIDs) with different error rates. If MPEG encoding is used,the I frames on CID1 may have a different packet error ratio (PER) and aless efficient UIUC and the B/P frames on CID2.

Another example could be a RS running a file transfer based on TCP and alatency sensitive streaming application simultaneously on two differentCIDs. The TCP connection can operate at a PER as high as, for example,30%, because it is not extremely delay sensitive, and the underlying MAClayer retransmission mechanism (ARQ/HARQ) or any other post transmissionlink adaptation mechanism can correct the errors and reduce the“residual error rate.” However, for the latency sensitive streamingapplication, the ARQ cannot operate due to latency constraints—implyingthat the PER should be much lower—say 1-5%.

IEEE 802.16 standards provide grants for the RS for UL transmission inthe UL MAP information elements (IEs). Each IE represents an allocationto a particular RS and specifies the number of UL slots for thisallocation, the beginning and ending offsets for this allocation, sothat the RS can uniquely identify the allocation. All of the allocationsto the RS, happen on the “Basic CID” (which is equivalent to a commoncontrol connection) of the RS.

The RS will not be able to able to decode the PER associated with the ULgrants and may use the grant with the higher PER for the applicationthat requires the lower PER. This may exacerbated by the fact that theUL channel may changing and the RS my not be able to adapt efficientlyto the changes because the BS processes the UL signals, except for thetime-varying UIUC values allocated by the BS in the UL grants.

IEEE 802.16 Standard defines Service flows as concept for managingtraffic over a wireless connection. The Service flows are mapped toconnections identified using CIDs for transporting data across the air.These flows are each scheduled based on the QoS parameters associatedwith them. However they do not indicate explicitly what type of trafficvoice, audio, video, data etc., is being utilized over it that mightindicate a particular target PER for proper operation.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are illustrated by way of example, and notby way of limitation, in the figures of the accompanying drawings inwhich like reference numerals refer to similar elements.

FIG. 1 is a block diagram of one embodiment of a wireless remote stationand a wireless base station.

FIG. 2 a is a conceptual diagram of time division duplexed (TDD) uplinkand downlink communications.

FIG. 2 b is a conceptual diagram of frequency division duplexed (FDD)uplink and downlink communications.

FIG. 3 is a flow diagram of one embodiment of communication of an uplinktarget PER from a base station to a remote station and uplinktransmission based on the target PER.

FIG. 4 is a diagram of one embodiment of communication of service flowmessages including a target PER.

FIG. 5 is a block diagram of one embodiment of an electronic system.

DETAILED DESCRIPTION

In the following description, numerous specific details are set forth.However, embodiments of the invention may be practiced without thesespecific details. In other instances, well-known circuits, structuresand techniques have not been shown in detail in order not to obscure theunderstanding of this description.

A described in greater detail below, in line with the IEEE 802.16 designphilosophy, the solution described herein may send the uplink grants ona “basic CID” as before. In one embodiment, the RS may be provided witha PER target for the UL grants, so that the RS may schedule either TCPor streaming or VOIP or other applications on the uplink grant, based onthe PER advertised in the uplink grant. In one embodiment, the PER maybe included in the UL map IE. In one embodiment, the UL MAP IE in theIEEE 802.16 specification may be changed to the following format.

TABLE One embodiment of a UL MAP IE structure with PER. CID 16 bits UIUC4 PER 8 If UIUC == 12{ OFDMA symbol offset 8 Sub channel offset 7 #OFDMA symbols 7 # subchannels 7 Ranging Offset 2 Reserved. 1 } else ifUIUC == 14 { CDMA-alloc-IE( ) 32 } else if UIUC ==15 { Extended UIUCdependent IE Variable } else { Duration 10 Rep coding indication 2 }Padding nibble, if needed 4

Packet Error Rate (PER) refers to the probability of the number of MAClayer packets that may be in error as a percentage on frame-by-framebasis. PER is a metric often used to decide whether to perform ARQschemes for MAC level retransmissions or post transmission linkadaptation schemes like Hybrid ARQ (HARQ) on a data transport connectionsignified by a connection identifier (CID) and directly one-to-onecorrespondent to a unique service flow identifier (SFID). PER targetsmay be used to infer the type of traffic (e.g., voice, audio, video,data) that is passing over the service flow. For example, voice packetstypically cannot tolerate more than 1% PER for reasonable quality. Datapackets, however, can operate with a higher PER with ARQ or HARQ schemesthat may improve the overall reliability of the transport.

In one embodiment, the UL map of Table 1 may include the elements asdefined in the IEEE 802.16 standards, which may be as set forth above ormay be different than the UL map of Table 1. Inclusion of PER dataallows information to be communicated between the BS and the RS that maybe used to allow the RS to provide a more efficient transmission of databased, at least in part, on the type of data.

The UL map structure of Table 1 may allow communication of PER databetween the BS and the RS. In one embodiment, the basic CIDs may be usedin the UL MAP IEs because, according to IEEE 802.16 standards, the BSshould not schedule on a per application-CID basis for the RS on the UL.The BS may provide a coarse grain allocation and the RS may determineallocations within this coarse grain allocation to schedule applicationCIDs.

IEEE 802.16 standard service flows have a target for a maximum trafficrate (bit rate) and also have service classes, for example, UnsolicitedGrant Service (UGS), Real Time Packet Service (RTPS) or Non-Real TimePacket Service (NRTPS) or Extended RTPS (ERTPS) that could support voiceactivity detection or Best Effort Service (BES) for managingprioritization of traffic. It is possible to use a combination ofpriority queues and schemes like HARQ for improving the performance ofthe transport over the air interface. For this to be even moreeffective, the techniques described herein using a target PER associatedwith every service flow may provide a parameter provided by theapplication layer to ensure that MAC layer operation is better finetuned and provide the desired traffic management results.

FIG. 1 is a block diagram of one embodiment of a wireless remote stationand a wireless base station. The example of FIG. 1 includes only asingle remote station for reasons of simplicity of description. A singlebase station may support any number of remote stations.

In one embodiment, remote station 110 may include remote station controllogic 130 coupled with media access controller 125. Remote stationcontrol logic 130 may include any combination of hardware, softwareand/or firmware that allow remote station 110 to function as a wirelessstation according to a pre-selected protocol (e.g., IEEE 802.16)including the use of PER as described herein. Media access controller125 may be any type of media access controller known in the art and maybe coupled with physical (PHY) link layer logic 120, which may becoupled with antenna 150.

In one embodiment, base station 170 may include base station controllogic 190 coupled with media access controller 185. Remote stationcontrol logic 190 may include any combination of hardware, softwareand/or firmware that allow remote station 170 to function as a wirelessstation according to a pre-selected protocol (e.g., IEEE 802.16)including the use of PER as described herein. Media access controller185 may be any type of media access controller known in the art and maybe coupled with physical (PHY) link layer logic 180, which may becoupled with antenna 160.

As described in greater detail below, remote station control logic 130and base station control logic 190 may communicate target PER values. Inone embodiment the target PER values may be communicated using basicservice flows as defined by the IEEE 802.16 standards. According tocurrent IEEE 802.16 standards, remote station 110 may determine thetarget PER for each service flow. In alternate embodiments, base station170 may determine target PER values.

FIG. 2 a is a conceptual diagram of time division duplexed (TDD) uplinkand downlink communications. In TDD communications each frame includes atime for downlink communications from the base station to the remotestation and a time for uplink communications from the remote station tothe base station. In a one to many configuration where one base stationcommunicates with many remote stations, the base station may determinethe portion of the frame (i.e., time period) that is allocated foruplink communications and the portion of the frame (i.e., time period)that is allocated for downlink communications. In addition todetermining the amount of time that is allocated for uplink and downlinkcommunications, the base station may determine other parameters, forexample, a target or average PER, modulation scheme, coding set, thatmay be used for the service flows supported. The modulation scheme maybe selected from, for example, QPSK, 16QAM, 64QAM, etc.

When engaged in downlink communications, the base station has sufficientinformation regarding the parameters of the service flows to matchdownlink data to provide efficient data transfer. However, unless theseservice flow parameters are communicated to the remote station(s),comparable efficiency for uplink data cannot be achieved. Using theuplink map described herein, parameters for uplink service flows may becommunicated to the remote stations, which may be used by the remotestations to provide more efficient data transfer than would otherwise bepossible.

If a remote station is allocated two service flows having differentPERs, the remote station may have sufficient information to matchapplications providing data for uplink transmission with service flowshaving differing parameters. For example, a remote station may have beenallocated two service flows, one with a PER of 1% and one with a PER of20%. The remote station may use the service flow with the PER of 1% forvoice traffic (e.g., Voice over IP) and the service flow with the PER of20% for a data transfer.

In one embodiment, the information transmitted from the base station tothe remote station via the UL map includes a PER value that correspondsto a target acceptable packet error rate as a percentage or as any othermeaningful indicator. Various parameters may be selected to achieve thedesired PER. For example, a modulation scheme and/or a coding set may beselected to achieve the desired PER based on wireless link conditions.These parameters may be dynamically modified periodically and/or asconditions change.

FIG. 2 b is a conceptual diagram of frequency division duplexed (FDD)uplink and downlink communications. In FDD communications each frameincludes a frequency for downlink communications from the base stationto the remote station and a frequency for uplink communications from theremote station to the base station. In a one to many configuration whereone base station communicates with many remote stations, the basestation may determine the portion of the frame (i.e., frequency range)that is allocated for uplink communications and the portion of the frame(i.e., frequency range) that is allocated for downlink communications.In addition to determining the frequencies that are allocated for uplinkand downlink communications, the base station may determine otherparameters, for example, a target or average PER, modulation scheme,coding set, that may be used for the service flows supported. The basestation and the remote station may communicate using FDD protocols asdescribed above with respect to service flow, or channel, target PERand/or other parameters.

FIG. 3 is a flow diagram of one embodiment of communication of an uplinktarget PER from a base station to a remote station and uplinktransmission based on the target PER. The functionality of the remote(possibly mobile) station and the base station may be implemented as anycombination of hardware, software and/or firmware. In one embodiment,communications between the base station and the remote station conformto the IEEE 802.16 standards; however, other wireless communicationsstandards may also be supported in a similar manner.

The remote station may receive data from a base station that includes atarget PER for a corresponding service flow, 310. The target PER may becommunicated in, for example, an uplink map information element. Inalternate embodiments, the target PER may be communicated in other datastructures.

In response to receiving the target PER, the remote station may selectone or more service flows for data to be transmitted to the basestation, 320. Control logic within the remote station may compare atarget PER for a service flow with a type of data to be transmitted(e.g., voice, file transfer, video) to provide an uplink transmissionwith a PER that provides efficient transmission of data based on thetype of data to be transmitted. The selected data may be transmittedfrom the remote station to the base station, 330.

In one embodiment, after the target PER for a service flow has beendetermined and/or communicated, the target PER may be dynamicallymanaged. In one embodiment, a Type Length Value (TLV) parameter that maybe referred to as a “Target PER TLV” may be used with Dynamic ServiceFlow Add Request (DSA-REQ) and Response (DSA-RSP) messages. The TargetPER TLV may also used in the Dynamic Service Flow Change Request(DSC-REQ) and Response (DSC-RSP) messages when target PER. In oneembodiment, the Target PER TLV may have the following format:

EXAMPLE Target PER TLV Type Length Value Scope PER-TV 1 byte 1-99(indicating %) DSA-REQ/RSP, DSC-REQ/RSPIn alternate embodiments, other data structures may also be used tocommunicate changes in target PER.

FIG. 4 is a diagram of one embodiment of communication of service flowmessages including a target PER. The example of FIG. 4 may allow thebase station and the remote station to communicate changes to a targetPER value. Either the base station or the remote station may initiatethe changes. In one embodiment, one or more of a Dynamic Service FlowAdd Request (DSA-REQ) message, a Response (DSA-RSP) message, a DynamicService Flow Change Request (DSC-REQ) message, and a Response (DSC-RSP)message as defined in the IEEE 802.16 standards may be used to carry thetarget PER TLV.

While the example of FIG. 4 illustrates each of the four messages listedabove, not all four are required to communicate changes in the targetPER. In one embodiment, a pair of messages (e.g., DSA-REQ and DSA-RESP,DSC-REQ and DSC-RESP) may be used to request and acknowledge changes tothe target PER. In an alternate embodiment, one of the messages (e.g.,DSA-REQ, DSC-REQ) may be used.

In response to receiving a change to the target PER, the receivingstation may send a response acknowledging the change and/or modify amapping of data to available service flows. In one embodiment, changesto the target PER may result in corresponding changes in modulationscheme and/or coding set. These changes may also be communicated usingthe messages listed above. These dynamic changes to the target PER for aservice flow may allow for more efficient transmission of data ascompared to use of a static PER.

FIG. 5 is a block diagram of one embodiment of an electronic system. Theelectronic system illustrated in FIG. 5 is intended to represent a rangeof electronic systems (either wired or wireless) including, for example,desktop computer systems, laptop computer systems, cellular telephones,personal digital assistants (PDAs) including cellular-enabled PDAs, settop boxes. Alternative electronic systems may include more, fewer and/ordifferent components. Electronic system 500 may operate as remotestation 110 or as base station 170 of FIG. 1.

Electronic system 500 includes bus 505 or other communication device tocommunicate information, and processor 510 coupled to bus 505 that mayprocess information. While electronic system 500 is illustrated with asingle processor, electronic system 500 may include multiple processorsand/or co-processors. Electronic system 500 further may include randomaccess memory (RAM) or other dynamic storage device 520 (referred to asmain memory), coupled to bus 505 and may store information andinstructions that may be executed by processor 510. Main memory 520 mayalso be used to store temporary variables or other intermediateinformation during execution of instructions by processor 510.

Electronic system 500 may also include read only memory (ROM) and/orother static storage device 530 coupled to bus 505 that may store staticinformation and instructions for processor 510. Data storage device 540may be coupled to bus 505 to store information and instructions. Datastorage device 540 such as a magnetic disk or optical disc andcorresponding drive may be coupled to electronic system 500.

Electronic system 500 may also be coupled via bus 505 to display device550, such as a cathode ray tube (CRT) or liquid crystal display (LCD),to display information to a user. Alphanumeric input device 560,including alphanumeric and other keys, may be coupled to bus 505 tocommunicate information and command selections to processor 510. Anothertype of user input device is cursor control 570, such as a mouse, atrackball, or cursor direction keys to communicate direction informationand command selections to processor 510 and to control cursor movementon display 550.

Electronic system 500 further may include network interface(s) 580 toprovide access to a network, such as a local area network. Networkinterface(s) 580 may include, for example, a wireless network interfacehaving antenna 585, which may represent one or more antenna(e). Networkinterface(s) 580 may also include, for example, a wired networkinterface to communicate with remote devices via network cable 587,which may be, for example, an Ethernet cable, a coaxial cable, a fiberoptic cable, a serial cable, or a parallel cable. In one embodiment,network interface(s) 580 may provide access to a network, for example,by conforming to IEEE 802.16 standards.

Reference in the specification to “one embodiment” or “an embodiment”means that a particular feature, structure, or characteristic describedin connection with the embodiment is included in at least one embodimentof the invention. The appearances of the phrase “in one embodiment” invarious places in the specification are not necessarily all referring tothe same embodiment.

While the invention has been described in terms of several embodiments,those skilled in the art will recognize that the invention is notlimited to the embodiments described, but can be practiced withmodification and alteration within the spirit and scope of the appendedclaims. The description is thus to be regarded as illustrative insteadof limiting.

1. A method comprising: generating, with a base station, a messagehaving an indication of a target error rate for a selected data transferflow, wherein the target error rate is different than a previous targeterror rate for the selected data transfer flow, wherein the base stationcommunicates with multiple remote devices; transmitting, according to awireless communications protocol that conforms to an Institute ofElectrical and Electronics Engineers (IEEE) 802.16 standard, the messageto a selected remote device having multiple service flows including atleast the selected data transfer flow via a basic data transfer flow,wherein the message includes parameters to be used for uplinkcommunications by the selected remote device; and transmitting, with theselected remote device, subsequent data via the selected data transferflow and not applying the target error rate to other service flows,according to the wireless communications protocol, using data transferparameters selected based, at least in part, on the indication of targeterror rate.
 2. The method of claim 1 wherein the one or more parametersto be used for uplink communications by the selected remote devicecomprise at least a target packet error rate (PER) for a correspondinguplink data channel.
 3. The method of claim 2 further comprisingselecting an encoding scheme based, at least in part, on the target PER.4. The method of claim 2 further comprising selecting a coding setbased, at least in part, on the target PER.
 5. A method comprising:receiving, from a base station communicating with multiple remotestations each having multiple service flows and according to a wirelesscommunications protocol that conforms to an Institute of Electrical andElectronics Engineers (IEEE) 802.16 standard, a message having anindication of a target error rate for a selected data transfer flow,wherein the target error rate is different than a previous target errorrate for the selected data transfer flow, wherein the message includesparameters to be used for uplink communications by the selected datatransfer flow; transmitting subsequent data via the selected datatransfer flow, according to the wireless communications protocol, usingdata transfer parameters selected based, at least in part, on theindication of target error rate and transferring data via other serviceflows using previous target error rates.
 6. The method of claim 5wherein the one or more parameters to be used for uplink communicationsby the selected remote device comprise at least a target packet errorrate (PER) for a corresponding uplink data channel.
 7. The method ofclaim 6 further comprising selecting an encoding scheme based, at leastin part, on the target PER.
 8. The method of claim 6 further comprisingselecting a coding set based, at least in part, on the target PER.
 9. Anarticle of manufacture comprising a non-transitory computer-readablemedium having stored thereon instructions that, when executed, cause oneor more processors to: generate, with a base station, a message havingan indication of a target error rate for a selected data transfer flow,wherein the target error rate is different than a previous target errorrate for the selected data transfer flow, wherein the base stationcommunicates with multiple remote devices; transmit, according to awireless communications protocol that conforms to an Institute ofElectrical and Electronics Engineers (IEEE) 802.16 standard, the messageto a selected remote device having multiple service flows including atleast the selected data transfer flow via a basic data transfer flow,wherein the message includes parameters to be used for uplinkcommunications by the selected remote device; and transmit, with theselected remote device, subsequent data via the selected data transferflow and not applying the target error rate to other service flows,according to the wireless communications protocol, using data transferparameters selected based, at least in part, on the indication of targeterror rate.
 10. The article of manufacture of claim 9 wherein the one ormore parameters to be used for uplink communications by the selectedremote device comprise at least a target packet error rate (PER) for acorresponding uplink data channel.
 11. The article of manufacture ofclaim 10 further comprising selecting an encoding scheme based, at leastin part, on the target PER.
 12. The article of manufacture of claim 10further comprising selecting a coding set based, at least in part, onthe target PER.
 13. An article of manufacture comprising anon-transitory computer-readable medium having stored thereoninstructions that, when executed, cause one or more processors to:receive, from a base station communicating with multiple remote stationseach having multiple service flows and according to a wirelesscommunications protocol that conforms to an Institute of Electrical andElectronics Engineers (IEEE) 802.16 standard, a message having anindication of a target error rate for a selected data transfer flow,wherein the target error rate is different than a previous target errorrate for the selected data transfer flow, wherein the message includesparameters to be used for uplink communications by the selected datatransfer flow; transmit subsequent data via the selected data transferflow, according to the wireless communications protocol, using datatransfer parameters selected based, at least in part, on the indicationof target error rate and transferring data via other service flows usingprevious target error rates.
 14. The article of manufacture of claim 13wherein the one or more parameters to be used for uplink communicationsby the selected remote device comprise at least a target packet errorrate (PER) for a corresponding uplink data channel.
 15. The article ofmanufacture of claim 14 further comprising selecting an encoding schemebased, at least in part, on the target PER.
 16. The article ofmanufacture of claim 14 further comprising selecting a coding set based,at least in part, on the target PER.